Symptoms include stand reduction, root rots, and basal stem decay Seed rot and pre-emergence damping-off are often credited to water damage. Taproots are usually dark brown, and small feeder roots are rotted or missing, on plants that survive the seedling phase. Stem discoloration, dark brown surface from the soil line up 6 inches, is less common on more tolerant/resistant varieties. Leaves on older plants become chlorotic, stunted and may wilt, die, turn brown, and remain attached to the plant for some time. This fungus survives as an “oospore” in infected crop debris. The oospore germinates in wet soils and releases many “zoospores” that swim to developing soybean roots and infect. Disease and infection is favored by wet conditions and soil temperatures near 60ºF. Low, poorly drained compacted soils, or soils with high clay content, or sites that are normally well-drained but wet, increase disease severity.

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URL:http://www.soybeans.umn.edu/crop/diseases/phytophthora_seedling_blight.htm

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